Method for determining organic materials in water

ABSTRACT

A method for estimating the amount and volatility of organic materials in contaminated water samples wherein a sample of the contaminated water is moved into a heated furnace and the vapors swept directly into a flame-ionization detector.

Uited States Patent [1 1 Eggertsen Aug. 21, 1973 METHOD FOR DETERMININGORGANIC MATERIALS IN WATER [56] References Cited [75] Inventor: Frank T.Eggertsen, Orinda, Calif. UNITED STATES PATENTS [73] Assignee: ShellCompany, New York NY 3,567,391 3/1971 Lysy et al. 23/253 PC Filed: J y1971 Primary Examiner--Morris O. Wo lk Assistant Examiner-R. E. Serwin 1N [2 1 App] 0 162,691 Attorney-Theodore E. Bieber et a].

Related US. Application Data [63] Continuation-impart of Ser. No.013,416, Feb. 24, [57] ABSTRACT 1970 abandoned A method for estimatingthe amount and volatility of organic materials in contaminated watersamples [52] 5:25 :32 wherein a sample of the contaminated water ismoved [51 1 Km Cl 1 33/18 Goln /20 into a heated furnace and the vaporsswept directly into 58 Field of Search 23/230 PC, 253 PC, a flame detect5 Claims, 7 Drawing Figures AMPLIFIER RECORDER INTEGRATOR 3o fi2| TEMP!PROG. 3'

42 sL/a fvo l mxms Al 5% 7 I CHAMBER fez I3 H2 2 Patented Aug. 21, 19733,753,654

3 Sheets-Sheet 1 AMPLIFIER RECORDER INTEGRATOR TEMP. PROG.

MIXI NiG CHAMBER l3 H2 N2 l NVENTOR F. T. EGGERTSEN Patented Aug. 21,1973 3,753,654

3 Sheets-Sheet 2 o BLANK DISTILLED WATER FURNACE l50 HEAT TO 550 L l l O5 I0 I5 20 TIME MINUTES CURVES FOR DISTILLED WATER AND STANDARDISOPROPYL ALCOHOL SOLUTIONS FIG. 3

0CD zzrm... FURNACE |soc HEAT TO 550C L l o 5 IO l5 v TIME MINUTESINVENTOR'. CURVE FOR on. m WATER F. T. EGGERTSEN FIG. 4

Patented Aug. 21, 1973 3,753,654

- 3 Sheets-Sheet 5 O 5 l0 I5 20 .T IME, MINUTES CURVE FOR STREET WATERFURNACE |5o HEAT T0 55o I I l 5 IO I5 20 TIME, MINUTES CURVE FOR SEAWATER FIG. 1

HEAT To 55o" L l I l o 5 l0 I5 TIME, MINUTES CURVE FOR REFINERY EFFLUENTINVENTORI PM 5 F. T. EGGERTSEN METHOD FOR DETERMINING ORGANIC MATERIALSIN WATER RELATED PATENT APPLICATION The present invention is acontinuation-in-part of application Ser. No. 013,416, filed Feb. 24,1970 now abandoned, which utilizes an apparatus similar to thatdisclosed in a copending application of the same inventor entitledMicroanalyzer for Thermal Studies, Ser. No. 617,337, filed Feb. 20, 1967now U.S. Pat. No. 3,574,549.

BACKGROUND OF THE INVENTION The present invention relates to a methodfor detecting small quantities of organic materials in water,particularly contaminated water samples taken from rivers, bays, planteffluents and similar bodies of water. The problem of pollution of watersupplies has increased in recent years and the need for quick andaccurate methods for determining the presence of contaminants isdesirable. In addition to the capability of handling a large number ofsamples, the process should be relatively low cost and simple'to'operatein order that relatively unskilled personnel may be employed inconducting analyses. Some of the most common pollutants of watersupplies are industrial products and wastes, particularly in thechemical and petroleum industries. As is well kwown, at times upsets orother casualties occur in processes that result in the dumping ofquantities of industrial products or the accidental discharge ofquantities of industrial products into water supplies or water-coveredareas, as for example, bays, rivers and such.

Normally, the pollutants are present in water supplies in very smallquantities, for example, in the range of a few parts per million (ppm)and thus sensitive equipment is required to effectively measure thequantity of pollutants. In the past various types of chromatographicdevices have been designed for detecting and measuring the quantity ofpollutants present in water supplies. While gas chromatographic devicesprovide a detailed analysis of the contaminants present in the watersample, they are limited to a determination of relatively volatileorganic material that can be eluted through the gas chromatographiccolumn. Also the chromatographic process separates the components sothat only the major contaminants are observed; minor components, each ata few parts per million, usually cannot be observed.

Other methods for determining organic carbon include: extractiontechniques to concentrate the contaminants, followed by various methodsof analysis; ox-

' idation techniques, followed by in infrared determination of CO, orCO; and a pyrographic method in steam carrier gas using a flameionization detector to determine the organic material. These methods areeither laborious or require rather elaborate equipment and/ortechniques.

SUMMARY OF THE INVENTION The present invention represents a simplerapproach to the determination of the organic contaminants in water andat the same time provides. a type of thermal analysis to differentiatethe contaminants according to volatility. Organic contaminants in watersamples are determined by utilizing a furnace to evaporate the sample ofthe water at a controlled rate. Control of the evaporation rate isnecessary in order to vaporize the sample rapidly, (for sensitivity andhigh speed of analysis) and yet is not vaporized so rapidly that thedetector does not operate properly. In the case of the flame ion izationdetector, too rapid vaporization may extinguish the detector flame. Thevapors evaporated with the water are transported to a detector that isspecific for organic materials to provide a measure of the volatileorganics. The furnace is then heated to a high temperature to volatilizethe remaining organic material, which is also determined by thedetector.

While the invention may use other types of detectors, hydrogenflame-ionization detectors .are particularly adaptable to the inventionbecause of their sensitivity to organic material and their lack ofresponse to water and other inorganic compounds. A suitable gas flowscheme is required for supplying hydrogen and air to the detector, and asuitable carrier gas. The invention may utilize nitrogen, hydrogen orvarious other carrier gases to sweep the evolved vapors into theflameionization detector.

The furnace used may be of various designs, for example, it may consistof a Vycor furnace closely coupled to the flame jet of the flameionization detector. The furnace should be capable of being heated atleast to 500C to volatilize the sample; and the flame ionizationdetector must be heated sufficiently to prevent condensation. of organicvolatiles enroute to the detector. The sample container may be aplatinum or other suitable vessel. It is held in a probe connected to apush rod to allow the sample to be inserted into the center of thefurnace.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be moreeasily understood from the following detailed,description of preferredembodiments when taken in conjunction with the attached drawings inwhich:

FIG. 1 illustrates an apparatus constructed according to this invention;

FIG. 2 illustrates the sample probe member in detail;

FIGS. 3-7 illustrate the analysis of various samples containing organiccontaminants.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, there isshown a furnace 10 which incorporates a heating means. The heating meansmay be a conventional resistance heater which is disposed or wound onthe outer surface of the furnace. The furnace may be formed of variousmaterials, for example, Vycor or other high temperature glass. Thefurnace incorporates suitable means for supporting a sample pan 11 and ameans for inserting and withdrawing the sample pan from the interior ofthe furnace. Details of a suitable retractable probe are shown in FIG.2. The furnace is provided with a gas inlet 12 through which a carriergas is supplied for sweeping the vapors evolved from the sample out ofthe furnace and into the detector. The gas inlet 12 is connected to asource of an inert gas, for example nitrogen 13. The nitrogen flows intoa mixing chamber 15 and from the mixing chamber to a valve 16 whichcommunicates with the inlet 12 of the furnace. The valve 16 is alsoprovided with an inlet for supplying air from a source 17 to the furnacein order that the furnace may be purged of contaminants to keep thesystem clean. Also connecting with the mixing chamber 15 is a means 14for introducing a suitable standard gas, for example butane, tocalibrate the response of the detector. For example, the means mayconsist of a septum which may be pierced by a hypodermic needle toinject measured amounts of the standard gas. The outlet 20 of thefurnace communicates directly with the detector 21 which is preferably aflame-ionization detector. The coupling of the furnace directly to thedetector is important since it substantially eliminates the condensationof evolved volatiles. The detector is supplied with a combustible gas,as for example pure hydrogen, from a source 22 at its lower end and isprovided with a burner tip 23 at its upper end. The detector jet 2] issupplied with suitable heating means to maintain its temperature at asuitably high level, preferably 500C, to prevent condensation ordeposition of volatiles evolved from the sample. Since flame-ionizationdetectors are well known, their construction and operation will not bedescribed further. The detector described in the abovereferencedcopending application could be used.

The two electrodes 32 and 33 of the flame-ionization detector arecoupled to an amplifier 34 in order that the signal may be amplified andthen supplied to recording equipment 35 and an integrator 37 if desired.As is well known, the quantity of material evolved from the sample asmeasured by the flame-ionization detector is related to the area underthe peak of the signal. Thus, it may be desirable at times to use anintegrator 37 to integrate the area under the peaks of the detectorsignal.

The temperature of the furnace is controlled by temperature controller30 which is coupled to the furnace by means of a lead 31. The actualtemperature of the furnace is measured by a thermocouple 36 which iscoupled to the recorder 35 in order that the temperature of the furnacemay be recorded in relation to or in correlation with the signal fromthe detector.

The probe is shown in detail in FIG. 2 and uses a rod 40 to support thesample pan 11 by means of a frame member 41. A thermocouple is disposedon the frame to measure the temperature of the sample pan. Thethermocouple lead 42 passes out through the center of the support rod.The support rod is a sliding fit in stopper 43 having a packing gland 44or other sealing means at one end. The outer surface of the stopper issealed to the furnace wall by means of an O Ring 45. An adjustable stop46 is provided for positioning the sample pan in the furnace.

OPERATION The temperature of the well-purged furnace is heated to apreselected temperature in the range of 50 180C by suitable adjustmentof the voltage to the heater windings. The pan containing the sample isinserted into the cool inlet of the furnace while the flame detector islit and gas flow established. The sample is then thrust into the furnaceto evaporate the water in the sample along with the lighter organic orhydrocarbon materials. The vapor from the sample pan will be conveyedfrom the furnace bythe inert gas flow and into the flame-ionizationdetector where any organic materials will be detected. By properselection of the initial furnace temperature the evaporation willproceed smoothly and will not interfere with the operation of the flamedetector. After the water and the light organic materials have beenevolved, the temperature of the furnace is raised to the desired maximumtemperature to evolve the remaining organic material from the sample.The heating rate can vary over a wide range, but is preferably rapid inorder to observe the volatiles as a sharp peak. Raising the temperaturefrom C to a maximum of 550C over a period of five minutes has been foundto give satisfactory results. A slower heating rate will, of course,provide a more precise measure of volatiles yields vs. temperature.

The organic content of the sample is determined from peak areas bymeasuring these areas (planimeter or integrator) and applying acalibration factor determined by analysis of a standard solution.Alternatively, the calibration factor can be determined by injecting astandard gas sample. Water reduces the detector response somewhat, andaccordingly a different calibration factor is applied to area obtainedduring the evaporation step from that for the l50550 heating step.

According to Hill and Newell (Nature, 206, 708 (1965) addition of watervapor to a carrier gas gradually reduced the carbon response of a flameionization detector until, with 10 percent water vapor the response wasreduced by 30 percent. In the present method the carbon response wasreduced by about 25 percent for organic material evolved duringevaporation of 50 u] of water at the rate of 10 ul per minute. Thecalibration factors are applied to the net areas, that is, the areasobtained above that for a distilled water blank. For amounts above a fewparts per million, the water blank is generally insignificant. The yieldof organic material may be broken down according to volatility, that is,volatile material evolved with the water and non-volatile materialobtained at higher temperatures. Also, a breakdown of the nonvolatilematerial may be obtained, if desired, by computing yield vs. temperaturedata from the curve obtained.

Referring now to FIGS. 3, 4, 5 and 6 and Table 1, there is shownrepresentative results with the instrument shown in FIG. 1 and describedabove. These analyses were made under the following conditions:

Carreir gas: nitrogen at 30 ml per minute Hydrogen for the detector, at25 ml per minute Sample size: 50 ml contained in platinum pan of 0.1

ml capacity Heating schedule: set voltage to heater windings for initialtemperature of 150C; after 5 to 8 minutes heat to 550in 5 minutesDetector: Modified Varian-Aerograph flame ionization detector, at 500C.

Sensitivity, 6X10A l mv.

Recorder: 1 mv =full scale FIG. 3 illustrates the recorded curve for apure water blank, as well as those for water containing trace quantitiesof a volatile organic compound, isopropyl alcohol. These curves showthat as little as 0.2 ppm of organic carbon can be observed above thepure water baseline. The results for various concentrations of isopropylalcohol shown in Table 1 demonstrate the accuracy of the method over theconcentration range 0.2 ppm to 22 ppm. The values shown were determinedusing the detector response calibration factor for butane and adjustmentof this factor according to the literature value for the response ofisopropyl alcohol relative to that for butane.

FIG. 4 illustrates application of the method of an oilcontaining samplemade by adding 9 ppm of an oil to distilled water and shaking themixture to disperse and dissolve the oil. The results shown areexpressed as parts per million of organic carbon based on calibrationwith butane. A small amount of non-volatile organic (0.5 ppm) wasobserved as well as 2.2 ppm of volatile material.

FIGS. 5, 6 and 7 show applicability of the method of a refineryeffluent, contaminated water from a city street and sea water from theSan Francisco Bay, respectively. The sea water was analyzed in admixturewith 40 mg of C-22 firebrick granules (42-60 mesh), which had been firedto red heat to destroy organic matter. The purpose of the firebrick wasto prevent spattering of the residual inorganic material as the sampleis dried; this spattering tends to produce fine salt particles which arecarried into the flame detector and produce a noisy signal.

TABLE 1 Analysis of Aqueous lsopropyl Alcohol Solutions Sample size: 501,]

Present, ppm Test Results, ppm

lsopropyl Alcoh Total C resulting loss in yield of organic carbonobserved in the flame ionization detector. The following tableillustrates the difference in results usng nitrogen and hydrogen ascarrier gases:

Organic Carbon ppm Carrier Volatile Non-volatile Distilled WaterNitrogen 0.1 0.2 Hydrogen 0.1 1.3 Tap Water Nitrogen 0.1 0.3 Hydrogen0.1 2.8

Sum corr. Beck- 4lJO for man Sample 110 400 600 Sum blank TOC Sea water(blank) 0. 2 0. 7 2.8 3. 5 2 Sea water plus fuel oil. 2. 2 2.8 6. 3 11.37. 8 10 Seawater plus crude 011. 1.6 9. 3 6. 3 17. 2 13. 7 14 Seawaterplus crude oil. 2. 3 8. 3 12. 4 23.0 19. 5 21 Nora-The Beckman TOCrefers to a total carbon analyzer mantl- Iactured by Beckman Instrumentsof Richmond, California.

I claim:

1. A method for estimating the amount and volatility of organicmaterials present in an aqueous solution, said method comprising:

charging a sample of the aqueous solution to a furnace while maintainingthe furnace at a temperature sufficiently high to vaporize all of saidwater at a controlled rate;

sweeping the 'vapor discharge from the furnace by means of a carrier gasdirectly to a detector capable of detecting organic carbon and supplyinga signal related thereto; recording the signal from said detector, toprovide a measure of the volatile organic material vaporized with thewater at said furnace temperature;

raising the temperature of the furnace at a programmed rate tovolatilize and/or pyrolyze residual organic matter in the sample;

recording the signal from the detector as the temperature of the furnaceis raised to provide a measure of the amount of said residual organicmatter.

2. The method of claim 1 wherein an inert gas is used to convey thesample through the furnace.

3. The method of claim 1 wherein the temperature of the furnace ismaintained at 50 to 180C when said water is supplied to said furnace andraised to about 500 to 800C when said residual organic matter isvolatilized.

4. The method of claim 1 wherein the detector is a hydrogen flameionization detector maintained at above 300C.

5. The method of claim 1 wherein the carrier gas is hydrogen.

2. The method of claim 1 wherein an inert gas is used to convey thesample through the furnace.
 3. The method of claim 1 wherein thetemperature of the furnace is maintained at 50* to 180*C when said wateris supplied to said furnace and raised to about 500* to 800*C when saidresidual organic matter is volatilized.
 4. The method of claim 1 whereinthe detector is a hydrogen flame ionization detector maintained at above300*C.
 5. The method of claim 1 wherein the carrier gas is hydrogen.